13.07.2015 Views

47.5 MB - The Whole Building Design Guide

47.5 MB - The Whole Building Design Guide

47.5 MB - The Whole Building Design Guide

SHOW MORE
SHOW LESS
  • No tags were found...

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Figure 3-65:<strong>The</strong> original modifiedbitumen membrane wasblown away after thegutter lifted in the areashown by the red arrow(the black membrane is atemporary roof). HurricaneFrancis (Florida, 2004)Special design attention needs to be given to attaching guttersto prevent uplift, particularly for those in excess of 6 inches inwidth. Currently, there are no standards pertaining to gutterwind resistance. It is recommended that the designer calculatethe uplift load on gutters using the overhang coefficient fromASCE 7. <strong>The</strong>re are two approaches to resist gutter uplift.m Gravity-support brackets can be designed to resist upliftloads. In these cases, in addition to being attached at itstop, the bracket should also be attached at its low end to thewall. <strong>The</strong> gutter also needs to be designed so it is attachedsecurely to the bracket in a way that will effectively transferthe gutter uplift load to the bracket. Bracket spacing willdepend on the gravity and uplift load, the bracket’s strength,and the strength of connections between the gutter/bracketand the bracket/wall. With this option, the bracket’s top willtypically be attached to a wood nailer, and that fastener willbe designed to carry the gravity load. <strong>The</strong> bracket’s lowerconnection will resist the rotational force induced by gutteruplift. Because brackets are usually spaced close togetherto carry the gravity load, developing adequate connectionstrength at the lower fastener is generally not difficult.m <strong>The</strong> other option is to use gravity-support brackets only toresist gravity loads, and use separate sheet-metal straps at 45-degree angles to the wall to resist uplift loads. Strap spacingMAKING CRITICAL FACILITIES SAFE FROM High Wind3-79

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!